RESEARCH ARTICLE Selenoprotein N-related myopathy: a retrospective natural history study to guide clinical trials Arpana Silwal1,a , Anna Sarkozy1,a, Mariacristina Scoto1,a, Deborah Ridout2,7, Anne Schmidt3, Aidan Laverty3, Matilde Henriques3, Luigi D’Argenzio1, Marion Main1, Rachael Mein4, Adnan Y Manzur1, Francois Abel3, Fouad Al-Ghamdi5, Casie A Genetti5, Didem Ardicli6, Goknur Haliloglu6, Haluk Topaloglu6, Alan H Beggs5 & Francesco Muntoni1,7 1The Dubowitz Neuromuscular Centre, Developmental Neuroscience Program, UCL Great Ormond Street Institute of Child Health, Great Ormond Street Hospital, London, UK 2Population, Policy and Practice Research and Teaching Department, UCL Great Ormond Street Institute of Child Health, London, UK 3Respiratory Department, Sleep and Non-Invasive Ventilation, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK 4Genetic Department, Molecular Genetics Laboratory Viapath, Guy’s Hospital, London, UK 5Division of Genetics and Genomics, The Manton Center for Orphan Disease Research, Boston Children’s Hospital, Harvard Medical School, Boston, MA 6Hacettepe University Children’s Hospital, Department of Paediatric Neurology, Ankara, Turkey 7NIHR Great Ormond Street Hospital Biomedical Research Centre, Great Ormond Street Institute of Child Health, University College London, Great Ormond Street Hospital Trust, London, UK

Correspondence Abstract Francesco Muntoni, Dubowitz Neuromuscular Centre, UCL Great Ormond Street Institute of Objective: To describe clinical features and disease progression of Selenopro- Child Health, 30 Guilford Street, London tein N-related myopathy in a large multicenter cohort of patients. Methods: WC1N 1EH. Tel: +44 02079052111; Fax: +44 Cross-sectional multicenter data analysis of 60 patients (53 families) with 02079052832; E-mail: [email protected] Selenoprotein N-related myopathy and single-center retrospective longitudinal analysis of 25 patients (21 families) over a median period of 5.3 years. Results: Funding Information The majority of patients (46/60, 77%) presented before age 2 years with hypo- This work was supported in part by The Muscular tonia, poor head/neck control, and developmental delay. At last assessment Dystrophy UK Central Grant to the DNC and by (median age 14 years; range 2.5 to 36 years), 10/60 patients had minimal or no grant MDA602235 from the Muscular Dystrophy ambulation. Ventilatory support was initiated in 50/60 patients at a mean Association (USA) and a generous gift from the Lee and Penny Anderson Family Foundation. Forced Vital Capacity (FVC) of 38% and at a median age of 13 years. Forty- Diagnostic DNA sequencing of patients in the five/60 patients developed scoliosis (at median age 12.1 years) and 18 had scol- Boston cohort utilized the resources of the iosis surgery at a median age of 13.6 years. Five children needed nasogastric Boston Children’s Hospital IDDRC Molecular feeds and/or gastrostomy. Longitudinal data analysis on 25 patients showed Genetics Core Laboratory funded by progressive decline of Hammersmith functional motor scores (estimated annual U54HD090255 from the US National Institutes of change À0.55 point), time to walk 10 meter, time standing from sitting, and Health. This research was also supported by the from lying. Sixteen patients had weights < 2nd centile. The estimated change in NIHR Great Ormond Street Hospital Biomedical À À À Research Centre. The views expressed are those FVC % per year was 2.04, with a 95% CI ( 2.94, 1.14). Conclusions: This of the author(s) and not necessarily those of the comprehensive analysis of patients with Selenoprotein N-related myopathy fur- NHS, the NIHR, or the Department of Health. ther describes the clinical course of this rare condition. The observed functional motor and respiratory data provide evidence of the slow decline patients experi- Received: 26 June 2020; Revised: 15 ence over time which is useful when considering therapeutic intervention. September 2020; Accepted: 20 September 2020

doi: 10.1002/acn3.51218 aThese authors equally contributed to the manuscript.

ª 2020 The Authors. Annals of Clinical and Translational Neurology published by Wiley Periodicals LLC on behalf of American Neurological Association 1 This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. Natural History of Selenoprotein N-related Myopathy A. Silwal et al.

Introduction patients were previously reported.6,8 All patients had a molecularly confirmed diagnosis of SELENON-RM with Selenoprotein N-related myopathies are recessive condi- two pathogenic SELENON variants in trans, identified tions caused by pathogenic variants in the SELENON 1-3 either by Sanger sequencing or next-generation sequenc- gene (previously known as SEPN1). The disease spec- ing (Table S1). trum includes congenital muscular dystrophy (CMD) Cross-sectional data were collected for 60 patients. with rigid spine, multiminicore disease, desmin-related Clinical data for patients from site N1 and N2 were col- myopathy with Mallory body-like inclusions and congen- 3-6 lected using a comprehensive medical questionnaire ital fiber-type disproportion myopathy, all sharing the (Table S2). Clinical data for patients from Site N3 were primary features of early-onset muscle weakness affecting available for more than one time-point and thus the most axial muscles, leading to early respiratory insufficiency.7-8 recent value was used for cross-sectional analysis, to make Selenoprotein N-related myopathies (SELENON -RM) 9 the information comparable among the three sites. are estimated to account for 11.65% of CMDs and 16% 10 Retrospective longitudinal clinical data were collected of congenital myopathies (CM) in the UK. The inter- 11,12 for patients from Site N3 only for the following parame- national standards of care for CMD and CM recom- ters: weight, motor function, respiratory function, and mend multidisciplinary follow-up for SELENON -RM Cobb angle. Motor function tests included The Hammer- and management of respiratory and orthopedic compli- smith standardized functional motor scores (HFMS),15 cations. timed 10 meters walk, timed raising from sitting, and Selenoprotein N, the protein product of the SELENON lying. Respiratory function measurements included gene, localizes in the endoplasmic/sarcoplasmic reticulum spirometry (forced vital capacity, FVC), performed in a (ER/SR) and interacts with SERCA2, the SR/ER pediatric lung function laboratory by experienced opera- Ca2 + pump, to keep it active within the relatively oxidizing 13 tors. The Global Lung Initiative dataset was used for ref- environment of the SR. The absence of Selenoprotein N erence.16 Sleep studies were performed in a pediatric sleep leads to a maladaptive ER stress response by oxidizing and 14 laboratory. Sleep-disordered breathing (SDB) was scored inhibiting SERCA2, adversely affecting muscle function. according to a standardized scoring system17. The use of ER stress inhibitors is being investigated as a pos- The project followed Caldicott Guardian regulations sible treatment for SELENON-RM and a clinical trial with and only anonymized de-identified aggregated patient N-acetylcysteine is ongoing (NCT02505087). Improved data were shared between the three sites. understanding of the pathogenesis of this condition fol- lowed by early therapeutic trials, make it necessary to better define the natural history and identify clinical endpoints to Statistical Methods support clinical trial readiness. Currently, no longitudinal Summaries are presented at the latest follow-up visit with SELENON studies on -RM have been reported. mean and standard deviation for normally distributed This study aims to provide deep phenotypic analysis data, and median and interquartile range for skewed data. and description of the disease course in a large multicen- For the cross-sectional cohort, Kaplan–Meier estimates SELENON ter cohort of -RM patients. In particular, we were calculated to describe the median time to scoliosis analyzed progression over time of motor abilities, respira- and ventilation. Frequency data are presented along with tory function, and scoliosis, aiming to identify clinical proportions and comparisons between groups, for exam- parameters to guide clinicians on disease timeline, and ple, diagnosis before or after 2 years of age were made provide information on prognosis, anticipatory care, and using a chi-squared test. For the longitudinal cohort tra- trajectories of functional changes, to help developing out- jectories for functional motor score, respiratory function, come measures for future clinical trials. and weight centiles over time were modeled using mixed- effects regression, accounting for the repeated measures Methods within patients. Estimated slopes are presented along with 95% confidence intervals. All statistical analyses were con- Sixty patients from (51 families) with SELENON-RM ducted in Stata v 15 (StataCorp. 2017. Stata Statistical were enrolled from three clinical sites: Site N1, Beggs Software: Release 15. College Station, TX: StataCorp LLC) Laboratory Congenital Myopathy Research Program, and a p value < 0.05 was deemed significant. Boston Children’s Hospital (Boston Children’s Hospital IRB protocol: 03-08-128) (22 patients) Site N2, Hacet- Results tepe University Children’s Hospital, Turkey (13 patients); and Site N3, Dubowitz Neuromuscular center Patients’ data and data availability are presented in (DNC), London, England (25 patients). Twenty-four Table S1 and Figure 1.

2 ª 2020 The Authors. Annals of Clinical and Translational Neurology published by Wiley Periodicals LLC on behalf of American Neurological Association A. Silwal et al. Natural History of Selenoprotein N-related Myopathy

Figure 1. Patients’ data availability in cross-sectional and longitudinal analysis. Flow diagram showing the number of patients for whom cross- sectional and longitudinal data is available for different investigations and assessment. Sites are indicated on the top. n: number; EMG electromyography; MRI muscle magnetic resonance imaging; NIV noninvasive ventilation; FVC Forced vital capacity; FVC% forced vital capacity percentage predicted; HFMS Hammersmith Functional motor score.

Cross-sectional data analysis Ambulatory function The age range of patients at last assessment was 2– Fifty of 60 patients (83%) were ambulant at last assess- 58 years (median 15 years, mean 16.5 years) with a male: ment (median age at last evaluation: 14 years; range 2.5 female ratio of 29:31. to 36 years). Four patients (two aged 13 and 15 years; age unknown for further two) were only able to take steps indoors holding furniture or walk with assistance. Eight Onset patients lost ambulation. Age at loss of ambulation was Age at onset ranged from birth to 13 years (mean known for four and was 6.6, 15, 16, and 18 years, respec- 2.3 years, median 9 months). Twenty-six of 60 patients tively (Fig. 2A). (43%) had onset ≤ 6 months with hypotonia and/or poor head/neck control. Twenty patients (33%) presented Orthopedic complications between 6 months and 2 years with gross motor delay, failure to thrive, and frequent respiratory tract infections; Scoliosis was reported in 45 of 60 patients (75%). The 14 patients (23%) presented> 2 years of age with motor median age at onset of scoliosis was 12.1 years (95% CI difficulties, scoliosis and/or failure to thrive. (9,14)) (Fig. 2B). Eighteen patients had spinal surgery at

ª 2020 The Authors. Annals of Clinical and Translational Neurology published by Wiley Periodicals LLC on behalf of American Neurological Association 3 Natural History of Selenoprotein N-related Myopathy A. Silwal et al.

AB C Proportion of patients fully ofambulant patients fully Proportion Proportion of patients without Proportion scoliosis Proportion ofProportion patients without ventilation

Age (years) Age (years) Age (years)

Figure 2. Cross-sectional data analysis for ambulation, scoliosis, and ventilation in SELENON-RM patients. Kaplan–Meier estimates for minimal/ noambulation (A), scoliosis onset (Cobbs Angle> 10°) (B), and initiation of ventilation (C) from birth. the median age of 13.6 years (range 9–17.6 years). Cobb’s swallow initiation in two patients. Two patients had angle range at the time of surgery, known for seven naso-gastric and one naso-jejunal feeds, and additional patients, was 50–77°. Six patients with Cobb’s angle range two patients underwent gastrostomy tube placement. A 15–72° were conservatively managed with spinal bracing. further patient was awaiting gastrostomy for persistent weight loss at the time of the last assessment at 7.4 years. Respiratory function Other features Fifty of 60 patients (83%) required ventilatory support from the median age 13 years (95% CI (11, 14), age Nasal intonation of voice was reported in 22/60 patients. range 1.6–50 years) (Fig. 1C). SDB prior to initiation of Facial weakness was observed in 20/60 patients, ptosis in ventilation was documented for 25/50 patients. Four seven, and ophthalmoplegia in one individual. patients developed respiratory insufficiency following recurrent chest infections (defined as> 3/year), aspiration II. Longitudinal data analysis pneumonia, or general anesthesia leading to initiation of respiratory support. Forty-eight of 50 patients were on Twenty-five patients from Site N3 (male:female ratio noninvasive ventilation (NIV), 46 on bilevel positive air- 12:13), aged 2.5–24 years at the last follow-up (median way pressure (BiPAP), and two on continuous positive 14 years), were assessed at more than one time point, for airway pressure ventilation (CPAP). Forty-four patients a median period of 5.3 years (range 1.6–17.8 years). Med- were on nocturnal NIV only, two needed additional sup- ian time from onset of symptoms to genetic diagnosis port during respiratory illness and further two during res- ranged from 5 months to 17.4 years. piratory illness and daytime as well. Two further patients had tracheostomy ventilation following acute respiratory Motor ability failure. Age at the start of ventilation was known for 46 patients. Thirty-five of 50 patients started ventilation Estimated annual change in the HMFS was À0.55 (95% before age 15 years (70%): 5 patients < 5 years, 7 CI (À1.05, À0.05)) (Fig. 3A, Fig S1), of timed 10 meter between 5–10 years, and 23 patients between 10–15 years. walk 0.16 sec (95 % CI (À0.03, 0.36)), of timed rise from The mean FVC percentage predicted (FVC%) at initiation floor sitting 0.86 sec (95 % CI (0.16, 1.55)), and of timed of ventilation was 38.3% (range 19–58%). rise from floor lying 0.87 sec (95 % CI (0.06, 1.68)) Three patients were recommended ventilator support, (Table S3). Seven children had post spinal surgery motor but this was refused by the family. Two of these three function follow-up data for a median of 8 months (range patients died at 10 and 18 years, respectively. The third 0.4 months–9 years) and all remained ambulant after sur- patient was last seen at age 7 years. Further seven patients gery. were not recommended ventilatory support at the time of their more recent follow-up, based on their last respira- Skeletal complications tory assessment (median age at last follow-up 7.3 years, range 2.5-14 years). Spinal stiffness preceding scoliosis was described in 21 of 25 patients (84%), from a median age of 10 years (range 2.0–15.6 years). The estimated change/year in Cobb’s Feeding angle was + 7.39 ° (95 % CI (1.70, 13.07)). Joint contrac- Ten patients had swallowing or chewing difficulty. Three tures were reported in 20 of 25 patients (80%), from a children had video-fluoroscopy that showed delayed median age of 12 years (range 0–16.5 years). Achilles

4 ª 2020 The Authors. Annals of Clinical and Translational Neurology published by Wiley Periodicals LLC on behalf of American Neurological Association A. Silwal et al. Natural History of Selenoprotein N-related Myopathy

B A Functional motor score Forced vital capacity % predicted capacity vital Forced

Age (years) D Age (years) C Weight Z scores Proportion of Proportion patients with FVC>40%

Age (years) Age (years)

Figure 3. Longitudinal analysis of functional motor score, respiratory function, and feeding in SELENON-RM patients. (A) population average model for the relationship between Hammersmith functional motor score and age along with 95% confidence intervals. Dots represent multiple visits per patient (n = 19). (B) Population average model for the relationship between Force Vital Capacity (FVC)% and age along with 95% confidence intervals. Dots represent multiple visits per patient (n = 23). (C) Kaplan–Meier estimates for time to FVC < 40%. (D) Line charts representing the progression of weight Z-Scores. Dots represent multiple visits per each patient (n = 21). tendons contractures were observed in 18 patients (75%), Results of polysomnography were available for nine of 25 of elbows in six (24%), and of knees in five (20%). patients. One patient had normal polysomnography at age 7.8 years, whereas eight showed hypoventilation from a mean age of 9.7 years (range 1.6–15 years). Sleep study data Respiratory function for five patients prior to BiPAP initiation showed elevated Median age at first FVC% recording was 12 years (range Apnea–Hypopnea Index (AHI); post NIV initiation follow- 5–15 years). Seventeen patients had FVC < 60% at first up studies showed a reduction in AHI. Initial BIPAP pres- recording. Estimated change in FVC%/year was À2.04 sures were adequate in two patients to overcome nocturnal (95% CI (À2.94, À1.14); Fig. 3B). Fourteen patients had hypoventilation with no need for further titration of pres- FVC < 40% (predictor of nocturnal hypoventilation)18 at sures. Four patients required increments on inspiratory pos- a median age of 14.8 years (95% CI (9.1–14.8)) (Fig. 3C). itive airway pressure during follow-up sleep studies to After initiation of NIV, yearly change in FVC% was overcome nocturnal hypoventilation. The increment on À1.15 (95% CI (À2.12, À1.17); P value 0.02). FVC% expiratory positive airway pressure was required in one decline following scoliosis surgery was estimated at À0.95 patient. Down titration on BiPAP pressures over the obser- (95% (CI À1.5, 1.5)). vation period was possible in two patients, both initiated on Recurrent chest infections were documented for 12 of 25 NIV at very young ages (3.2 years and 6.7 years) (Fig S2). patients (48%) from a median age of 5 years (3 months– Based on our data we estimated the number of patients 14 years) and 10 of these patients needed NIV from a med- required to run future clinical trials in which FVC is one of ian age of 6 years (1.6–14 years). Three patients had recur- the endpoints. A clinical trial, in which further progression rent chest infections, whereas on NIV and two of the three of respiratory decline is completely abolished over a 12- needed daytime ventilator support as well. The cough assist month period, would require 50 patients for 80% power. machine was used by 3/25 children. On the other hand, a therapeutic intervention that could

ª 2020 The Authors. Annals of Clinical and Translational Neurology published by Wiley Periodicals LLC on behalf of American Neurological Association 5 Natural History of Selenoprotein N-related Myopathy A. Silwal et al. decrease disease progression by 75%, that is, reducing the Muscle ultrasound evidenced increased echogenicity in average yearly decline of 2% to 0.5%, would require about quadriceps femoris in all investigated patients (not shown). 80 patients for 80% power (Fig. 4). Electromyography showed myopathic changes in ten patients. Five patients had muscle MRI of lower limbs evidencing selective sartorius muscle involvement (not Weight shown). Muscle biopsies revealing both dystrophic and At first assessment, 10 children (aged 1–15 years, mean myopathic changes, often with accompanying minicores 10.5 years) had weights below the 2nd centile. By the last fol- or core-like areas. One patient’s muscle exhibited Mallory low-up, 16 of 21 patients (76%) had weight below the 2nd body inclusions (Table S1). centile. Eighteen patients had weight < 50th centile Twenty-four patients were compound heterozygous (Fig. 3D). Fall in weight centiles coincided in some patients and 36 homozygous for SELENON gene pathogenic/likely with respiratory decline (abnormal sleep study, chest infec- pathogenic variants. Thirty-two individuals had missense tions and/or NIV initiation), progressive scoliosis, or spinal variants (in homo or compound heterozygosity), 20 a loss surgery. The population average model graph showed an of function variant (frameshift, stop or splice site) and average annual change in weight z scores of 0.65 eight a combination of the two. The c.943G> A (P = 0.008). Two children, after an initial period of low p.(Gly315Ser) missense change was the most common weight centiles, presented weight increased> 91st centile, in variant, present in homozygosity in seven patients and in parallel to a reduction of their motor abilities. compound heterozygosity in 10.

III. Investigations IV. Genotype and phenotype correlation analysis Creatine kinase (CK) levels were within normal limits in 39 patients (76%) and moderately elevated in 12 (median 477 We compared phenotypes of patients with either two loss U/L, range 236–1505 U/L). One patient with CK of 2459 U/ of function mutations, two missense variants or a combi- L was a heterozygous female carrier of a nonsense DMD nation of one loss of function and one missense muta- gene variant (c.2348A> C; Ref sequence LRG_199t1). tion. No clear association was seen between the type of

Observed Time 25% 50% 75% 100% FVC% frame restoration restoration restoration restoration decline Annual -2.04 -1.53 -1.02 -0.51 0 change

Level of restoration

Figure 4. Estimated statistical power and sample sizes to detect restoration in decline of Forced Vital Capacity % predicted in SELENON-RM cohort.

6 ª 2020 The Authors. Annals of Clinical and Translational Neurology published by Wiley Periodicals LLC on behalf of American Neurological Association A. Silwal et al. Natural History of Selenoprotein N-related Myopathy mutation and age at onset of symptoms, ambulation, fre- function, with in particular only 2/41 (5%) nonambulant quency of scoliosis, and NIV or median age at start of patients reported in one of the previous studies7-8,19.We ventilation (data not shown). provide for the first time longitudinal functional data We then subdivided the entire cohort of patients based analysis and disease course for SELENON-RM patients, on age at onset ≤ 2 and> 2 years. Patients present- focusing on respiratory, and functional scores over time. ing ≤ 2 years had onset of scoliosis at a median age of Previous studies suggested that age at onset, clinical 10 year versus 14.3 years in the> 2 year group (Fig. 5A). severity, and course of disease were independent vari- Loss of ambulation occurred earlier in patients with ables.7-8 However, our observation of earlier loss of onset ≤ 2 years. Among these, six children with minimal ambulation and onset of scoliosis in patients with earlier or no ambulation had symptom onset < 1 year. No dif- age at onset suggests a correlation between these vari- ference was observed in the age at the start of ventilation ables (Fig. 5A). between the two groups (Fig. 5B). No statistical analysis Our estimate of yearly decline in FVC% (À2.04 before was performed due to the limited numbers of patients. NIV, À1.15 after initiation of ventilation), differs from We reviewed age at onset, presentation, and disease previous reports, indicating relative stability of respiratory course in the nine sib pairs of this cohort. Age at onset function over time.7,20 Our estimates were calculated over was dissimilar in one sib pair, with the older child pre- a longer period of time and this might explain the senting at birth and the younger at age 4.5 years. In two observed differences. A 5% change/year in FVC% is further sib pairs, BiPAP was initiated at an earlier age in defined as a minimally clinically significant change in the the younger siblings. In view of the small number of fam- DMD population.21 Extrapolating this to our SELENON- ilies, no statistical analysis was performed on these find- RM cohort, we can estimate an average decline of 5% in ings. FVC% after 2.5 years. Considering the severity of respira- tory involvement in SELENON-RM patients, longitudinal Discussion assessments of FVC could represent an effective outcome measure to demonstrate progression over time, in chil- In this study, we comprehensively describe cross-sec- dren where it can be reliably performed. We also provide tional and longitudinal clinical and functional data in a for the first time power analysis for future clinical trials large cohort of SELENON-RM patients. The cross-sec- in which FVC would be used as one of the endpoints tional study not only confirms early onset with hypoto- (Fig. 4). nia, with high frequency of poor neck/head control, This large cohort analysis confirms survival into adult- spinal rigidity, progressive scoliosis, and need for early hood for the majority of patients provided with adequate respiratory support in SELENON-RM patients, but also respiratory and orthopedic management and treatments.22 describes the frequency of additional complications and Previous reports indicate a relative stability in motor features such as swallowing difficulties and ptosis. the function over time in SELENON-RM patients.7-8 In higher frequency of patients with minimal or no ability absence of a motor scoring scale validated for SELENON- to walk (17%) contrasts with earlier reports, which RM, we used the HFMS previously validated in pediatric focused on function group of patients with better motor neuromuscular conditions.15 Our results highlight a

AB

Early symptom onset late symptom onset Early symptom onset late symptom onset

Figure 5. Time to event analysis for scoliosis and ventilation need according to onset. Survival curves for scoliosis (A) and ventilation free probability (B) of patients with onset of symptoms ≤ 2 years (early symptom onset, blue line) and> 2 years (late symptom onset, red line).

ª 2020 The Authors. Annals of Clinical and Translational Neurology published by Wiley Periodicals LLC on behalf of American Neurological Association 7 Natural History of Selenoprotein N-related Myopathy A. Silwal et al. modest annual decline in HFMS (À0.55 points/year in his group), who unfortunately passed away during the children> 5 years). A similar modest, but clear decline course of this study. We acknowledge the contribution of was also noted for timed tests. Overall, the motor decline the Highly Specialised Service for Congenital muscular appears to parallel scoliosis progression, weight fluctua- dystrophies and congenital myopathies at the Dubowitz tions, and respiratory decline. Neuromuscular Centre and in particular Dr Lucy Feng Failure to thrive, reported in up to 57% of reported for her assistance. We thank Dr Stephanie Robb, Dr Ros SELENON-RM patients3,7-8,12. was also frequently ob- Quinlivan, and Dr Pinki Munot and the Neuromuscular served in this cohort, with 76% of patients with Physiotherapy team for the clinical assessment of our weights < 2nd centile at the last follow-up. Interestingly, patients at DNC and the Great Ormond Street Lung while dietary supplementation helped to increase weight physiology team for spirometry data. centiles, in two children steep weight gain was observed in parallel with the decline in motor abilities, one of the two being at the more severe end of the phenotypic Conflicts of Interest spectrum. The European Society for Paediatric Gastroen- Dr. Beggs serves on the scientific advisory boards of terology, Hepatology and Nutrition consensus statement Audentes Therapeutics Inc and Dynacure Inc., has on diagnosis and management of gastrointestinal and received sponsored research support from Audentes nutritional complications in children with neurological Therapeutics Inc, receives sponsored research support 23 impairment suggests that weight, height, body mass from Alexion Pharmaceuticals, Inc., is a paid consultant index, height-for-age, weight-for-age are poor predictors for F. Hoffmann-La Roche, performs occasional paid of body composition and lead to misinterpretation of consulting for Guidepoint Global Advisors and Gerson low body mass index values and/or low weight z-scores Lehrman Group, Inc., and receives research support leading to overfeeding. Further research is needed to bet- from the US National Institutes of Health and the Mus- ter evaluate body composition in SELENON-RM patients cular Dystrophy Association. There are no disclosures (including whole body Dual-energy X-ray absorptiometry from other authors. analysis) and to assess nutritional status to develop a dis- ease-specific growth curve. References In the patients studied, we did not observe any obvious 1. Dubowitz V. Rigid spine syndrome: a muscle syndrome in genotype–phenotype correlations, confirming previous search of a name. Proc R Soc Med 1973;66:219–220. observations.7-8 2. Moghadaszadeh B, Desguerre I, Topaloglu H, et al. Our current study has some limitations. Patients were Identification of a new locus for a peculiar form of assessed in three clinical sites and although we followed the congenital muscular dystrophy with early rigidity of the International standards of care guidelines, different clinical spine, on chromosome 1p35–36. Am J Hum Genet protocols were used and standards of care have evolved over 1998;62:1439–1445. time. This study presents a mix of cross-sectional and longi- 3. Moghadaszadeh B, Petit N, Jaillard C, et al. Mutations in tudinal data analysis, with limited longitudinal observations. SEPN1 cause congenital muscular dystrophy with spinal Our real-world study also stresses the importance to collect rigidity and restrictive respiratory syndrome. Nat Genet data according to standardized assessment tools and clini- 2001;29:17–18. cally meaningful end points and outcome measures to guide 4. Ferreiro A, Quijano-Roy S, Pichereau C, et al. Mutations clinicians and researchers on disease monitoring and plan- of the selenoprotein N gene, which is implicated in rigid ning of therapeutic clinical trials. spine muscular dystrophy, cause the classical phenotype of In conclusion, our study expands the knowledge on the multiminicore disease: reassessing the nosology of early clinical course of patients with SELENON-RM and pro- onset myopathies. Am J Hum Genet 2002;71:739–749. vides longitudinal data for patients affected by this condi- 5. Ferreiro A, Ceuterick-de Groote C, Marks JJ, et al. tion. The observed functional motor and FVC trend data Desmin-related myopathy with Mallory body-like provide evidence for a slow decline over time. Our results inclusions is caused by mutations of the selenoprotein N emphasize the importance of robust and consistent multi- gene. Ann Neurol 2004;55:676–686. disciplinary management of SELENON-RM patients to 6. Clarke NF, Kidson W, Quijano-Roy S, et al. SEPN1: improve outcomes and inform clinical trials. associated with congenital fiber-type disproportion and insulin resistance. Ann Neurol 2006;59:546–552. Acknowledgments 7. Schara U, Kress W, Bonnemann CG, et al. The phenotype and long-term follow-up in 11 patients with juvenile Special thanks and appreciation to Dr Nigel Clarke (two selenoprotein N1-related myopathy. Eur J Paediatr Neurol of the patients in the cohort were previously reported by 2008;12:224–230.

8 ª 2020 The Authors. Annals of Clinical and Translational Neurology published by Wiley Periodicals LLC on behalf of American Neurological Association A. Silwal et al. Natural History of Selenoprotein N-related Myopathy

8. Scoto M, Cirak S, Mein R, et al. SEPN1-related 20. Caggiano S, Khirani S, Dabaj I, et al. Diaphragmatic myopathies: clinical course in a large cohort of patients. dysfunction in SEPN1-related myopathy. Neuromuscul Neurology 2011;76:2073–2078. Disord 2017;27:747–755. 9. Sframeli M, Sarkozy A, Bertoli M, et al. Congenital 21. McDonald CM, Gordish-Dressman H, Henricson EK, muscular dystrophies in the UK population: Clinical and et al. Longitudinal pulmonary function testing outcome molecular spectrum of a large cohort diagnosed over a 12- measures in Duchenne muscular dystrophy: long-term year period. Neuromuscul Disord 2017;27:793–803. natural history with and without glucocorticoids. 10. Maggi L, Scoto M, Cirak S, et al. Congenital myopathies- Neuromuscul Disord 2018;28:897–909. clinical features and frequency of individual subtypes 22. Sponholz S, von der Hagen M, Hahn G, et al. diagnosed over a 5-year period in the United Kingdom. Selenoprotein N muscular dystrophy: differential diagnosis Neuromuscul Disord 2013;23:195–205. for early-onset limited mobility of the spine. J Child 11. Wang CH, Bonnemann CG, Rutkowski A, et al. Neurol 2006;21:316–20. Consensus statement on standard of care for congenital 23. Romano C, van Wynckel M, Hulst J, et al. European muscular dystrophies. J Child Neurol 2010;25:1559–1581. Society for Paediatric Gastroenterology, Hepatology and 12. Wang CH, Dowling JJ, North K, et al. Consensus Nutrition guidelines for the evaluation and treatment of statement on standard of care for congenital myopathies. J gastrointestinal and nutritional complications in children Child Neurol 2012;27:363–382. with neurological impairment. J Pediatr Gastroenterol 13. Marino M, Stoilova T, Giorgi C, et al. SEPN1, an Nutr 2017;65:242–64. endoplasmic reticulum-localized selenoprotein linked to skeletal muscle pathology, counteracts hyper-oxidation by Supporting Information means of redox-regulating SERCA2 pump activity. Hum Mol Genet 2015;24:1843–1855. Additional supporting information may be found online 14. Pozzer D, Varone E, Chernorudskiy A, et al. A in the Supporting Information section at the end of the maladaptive ER stress response triggers dysfunction in article. highly active muscles of mice with SELENON loss. Redox Biol 2018;20:354–366. Figure S1. Changes over time in Hammersmith Func- 15. Scott OM, Hyde SA, Goddard C, Dubowitz V. tional motor score. Individual functional motor score pat- Quantitation of muscle function in children: a prospective tern over time. The maximum functional motor score = study in duchenne muscular dystrophy. Muscle Nerve being 40/40. Lines represent individual patients (n 19). 1982;5:291–301. Figure S2. Changes over time in noninvasive nocturnal 16. Quanjer PH, Stanojevic S, Cole TJ, et al. Multi-ethnic bilevel positive airway pressures. Data for seven patients reference values for spirometry for the 3–95-yr age range: are presented. Intervals between cardiorespiratory sleep the global lung function 2012 equations. Eur Respir J studies on the x-axis differed between patients. Required 2012;40:1324–1343. levels of expiratory airway pressure (EPAP) and inspira- 17. Berry RB, Brooks R, Gamaldo CE, et al. The AASM tory airway pressure (IPAP) are displayed on the y-axis.. Manual for the Scoring of Sleep and Associated Events: Table S1. Characteristics and progression of patients with Rules, Terminology and Technical Specifications, Version SELENON-RM. 2.0.3.www.aasmnet.org, Darien, Illinois: American Table S2. Data collection form for site N1 and N2. Academy of Sleep Medicine 2014. Table S3. Yearly Progression of timed rise from floor sit- 18. Ragette R, Mellies U, Schwake C, Voit T, Teschler H. ting and lying, in second. Patterns and predictors of sleep disordered breathing in primary myopathies. Thorax 2002;57:724–728. 19. Ardissone A, Bragato C, Blasevich F, et al. SEPN1-related myopathy in three patients: novel mutations and diagnostic clues. Eur J Pediatr 2016;175:1113–1138.

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